FGF21 can stimulate the hypothalamic-pituitary-adrenal axis to promote liver gluconeogenesis, ketogenesis, and fatty acid oxidation during fasting.FGF21 in AT-exos can increase heat production and accelerate the development of beige adipocytes under cold stimulation. And the BAT-derived FGF21 has an endocrine regulatory function to reduce cardiac hypertrophy. The gene discussed is FGF21; the disease is cardiac hypertrophy.